I think my answer was a bit ambiguous.
An EOG car contains two components. A diesel generator to generate electricity and another system to step down this voltage and distribute it to the rake. In case of HOG, the electricity is generated by the loco itself, but some system is still needed to step down the voltage and distribute it to the coaches. This is achieved using what is called a power car ( basically a coach with a transformer). Since the power car only has to distribute the power, one is sufficient for one rake.
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more... In case of the Kalka Shatabdi, instead of building a new power car, they just took the existing EOG cars in the rake and disabled the diesel generator, using only the distribution system to distribute power from the loco to the rake. That's why, even if it is running with EOG cars, it is very likely that the diesel generator is not running and the rake is running on HOG. Here is a document where it is explicitly mentioned that the modified power cars are being used on the KLK shatabdi.
click here